Key

Items are BOLD.

Locations are UNDERLINED.

Pokemon Diamond, Pearl, Platinum Walkthrough:

Mt. Coronet

Spear Pillar

Route 222

Mt. Coronet

Before going, make sure to stock up on lots of Ultra Balls. Also be sure to have lots of Dusk Balls, which can be found
in Pastoria City's Pokemon Mart. The reason is that you'll soon be catching Dialga/Palkia. In addition, you might need (Super/Max)
Repels if you don't want to encounter wild Pokemon every few steps. You'll also need a Pokemon that knows Rock Climb. Now fly
over to Oreburgh City and head east, entering Mt. Coronet on Route 207.

Surf across the water at the north. Go up the stairs and pick up the Protein. Climb the rocks at the very east and go up the steps.
Pick up the Max Potion at the north and also the hidden Ether on the small piece of rock nearby. Go all the way south for an
Escape Rope. Go north, then south again. Get outside through the exit temporarily, climb down the rocks, and pick up an Iron.
Go back into the mountain and go as far north as you can. Cross the bridge and go south for TM80 - Rock Slide. Go north for a Revive.
Now head east to get to the lower level and go inside the cave opening. Go up the steps and you'll be surrounded by three steps on all sides. Take
the one on the right for a hidden Max Revive on the southern-most rock. Go back and go north, where you'll battle a Galactic Grunt. Go
west and pick up the hidden Super Repel on the corner rock. Fight the Grunt and exit through the south.

Climbing to the Peak

Now you're outside in a snowy environment. The goal now is to climb to
the top of Mt. Coronet. Go east, north, and climb the rocks. If you go east into the cave opening, you can go straight up the steps for
a hidden Ultra Ball. Smash the rock at the bottom-left corner and pick up the hidden PP Up on the rock that's revealed. Go
outside, head west, then south (not through the grassy area). Push the boulder out of your way and continue west. Smash the rock along the way
and pick up the hidden Max Potion. Head north and go into the cave opening. Back inside, go straight and climb the rocks. Battle the
Galactic Grunt, smash the rock near him, and pick up the hidden Revive. There's also a hidden Ether on a northern rock. Go east,
battle the Grunt, and go south a bit to pick up a hidden Escape Rope. Head out again by going east.

Go all the way north for a hidden Rare Candy on the single rock. Go south a bit and go down the steps. Check out the cave opening to battle
some Galactic Grunts and pick up a few hidden items, including a Rare Candy hidden in one of the rocks in the lowest level. You won't be
able to go into the cave opening blocked by the Galactic Grunt. After they leave later, however, you may go inside to pick up TM02 - Dragon Claw.
After that, get out of this cave area.

From the outside, climb the rocks westward and head west. You'll find a TinyMushroom hidden on a rock and a Big Mushroom on the
northern-most level. You'll soon see another cave opening, which you should enter. On the second rock, you'll find another TinyMushroom.
Keep going east and head up the steps. Battle the Galactic Grunt and pick up the hidden Max Potion behind her. If you go south as far as you
can, you'll be able to pick up a hidden Stardust on a rock. Fight the Grunt and head west up the steps. As you go north from here, you'll
battle one last Grunt before finally reaching the peak of Mt. Coronet.

At the top, you'll battle two Galactic Grunts before you get to the
final challenge. Walking forward, you'll find Commander Cyrus, Commander Mars, and Commander Jupiter all in one spot! Commander Cyrus will
summon Dialga (in Pokemon Diamond)/Palkia (in Pokemon Pearl). As the beast comes out, you'll see some impressive animation sequences. After Cyrus is done talking,
walk forward and Commander Mars will challenge you to a battle. Suddenly, Rival comes over and gets into battle stance with Commander Jupiter.
A challenging double battle will ensue (challenging mainly because Rival's Pokemon doesn't seem to help much). After defeating the two of them,
Rival will heal your Pokemon and you'll observe Dialga/Palkia forming a galaxy as instructed by Cyrus. Luckily, the Legendary Trio will arrive to mess
up his plans. Furious, Cyrus will battle you one-on-one with some pretty powerful Pokemon. After defeating him, the Team Galactic will leave,
and Professor Rowan and Dawn will come. Professor Rowan tells you to help Dialga/Palkia out and the way to do that is to capture it (or defeat it)!
The time has come...

Before going for Dialga/Pearl, save your game! Also, note that you should NOT use
your Master Ball. This Pokemon is easier to capture than other legendaries in the game. Dialga/Palkia is at lv. 47 and it's very strong.
Dialga is a Steel/Dragon-type Pokemon and Palkia is a Water/Dragon-type Pokemon. Try to get its HP as low as possible and throw Ultra
Balls and Dusk Balls at it (while listening to the wonderful background music). Once you have captured it, Professor Rowan will
come over to praise you on your incredible feat. Afterwards, go all the way north to pick up either the Adamant Orb (Diamond)
or Lustrous Orb (Pearl), which powers up Dialga and Palkia, respectively.

Now, you'll be able to catch the Legendary Trio by re-visiting the three lakes. Be sure to have plenty of Dusk Balls, since these
are the best types of Balls to use on these legendaries.

Surf to the south-west section to pick up TM38 - Fire Blast.
Then, surf to the center of the lake and go into the cave. Inside, you'll see Mesprit. Press "A" against it and you'll see a picture of it,
which will be logged in your PokeDex. Unfortunately, it'll fly away immediately. Professor Rowan then comes running over to tell you to
use the Marking Map on your Poketch to track Mesprit's location. Like the Legendary Beasts of Pokemon
Gold/Silver/Crystal, you'll have to walk in the grassy areas where Mesprit is detected in hopes of encountering it. Note that if you encounter
it, Mesprit will flee immediately after you make any move. So, if you want to capture it, you probably should prevent it from fleeing, using
a move such as Mean Look.

Azlef at Lake Valor

Surf to the south-east section to pick up TM25 - Thunder. Then,
surf to the center of the lake and go into the cave. Unlike Mesprit, Azlef will actually battle you; in other words, you can capture it right
now! However, be careful, since this Pokemon is quite strong (lv. 50 with high damaging moves) and harder to catch than Dialga/Palkia.

If you haven't done so already, surf to the north-east section to pick up
TM14 - Blizzard. Once again, go into the cave at the center of the lake. Inside, you'll be able to catch the lv. 50 Uxie.

After all of that, we shall continue through the game. You only have one more Gym and the Elite 4 to take care of before the end of this wonderful
game (of course, there's lots more stuff to do afterwards). Fly over to Pastoria City and go east, past the hotel. When you're on
Valor Lakefront, continue east past the part that was previously blocked by a fat guy, and you'll arrive on Route 222.

There are tons of trainers to battle on Route 222, many of them optional. This is because there is a fork in the route. The northern
fork has more trainers that you'll be forced to battle with, while the southern fork has optional Fishermen. Take either, or both, since both
forks eventually combine. On the north side, you can get a whole bunch of Berries at the beginning. Other than battling trainers, you'll
be able to pick up a Honey, a hidden Ultra Ball, and a Carbos (very east side of the northern fork after cutting a tree).
Also, talk to the person facing south for TM56 - Fling. At the end of the south side, smash the rock and go onto the raised area to
pick up a hidden Honey. If you surf east a little and get back on land, you can pick up a hidden Big Mushroom.